2019 ASHS Annual Conference

Peach is the third most important temperate tree fruit in the world after apple and pear. According to FAOSTAT, world peach production in 2017 reached over 24.6 million tons, with the U.S. being the fifth producer in the world with approximately 775,189 tons. However, peach consumption per capita has decreased over the last decade, most likely due to inconsistent quality of the fruit on the market. Many peaches have excellent quality picked fresh from the tree (at harvest), but after being held in cold storage, the peaches can develop storage disorders and/or chilling injury (CI) symptoms such as mealy texture, brown flesh, loss of flavor, and development of ‘off flavors’. Therefore, maintenance of fruit quality after cold storage is a high priority. Susceptibility to postharvest disorders is highly influenced by genetic background. Fortunately, peach germplasm that is less susceptible to CI exists and can be used in new cultivar development. To understand the genetic background of CI development during cold storage we performed a genome wide association study (GWAS) using GModel on a total of 426 individuals from three public fresh market peach breeding programs (University of Arkansas, Texas A &M University, and Clemson University). The material was genotyped with the new Illumina 9+9K SNP peach array and phenotyped for: Bleeding (BL), Expressible Juice (EJ), Browning (BRO), Texture (TEX) and Mealiness (ME) in two seasons (2015 and 2016). GWAS revealed 122 markers in all chromosomes associated with these postharvest traits. TEX and ME were positively correlated and associated with markers on linkage groups (LGs) 1, 3, 5, 6 and 7. A SNP marker associated with all measured post-harvest traits was detected on LG4, and one associated with four of the traits (EJ, BRO, TEX and ME) was detected on LG6. Candidate gene analysis within the haploblock regions encompassing the associated markers on LG4 and 6 identified 14 and 15 predicted genes, respectively. Functional annotation of these 29 predicted genes classified them within the following GO terms: metabolic process, antiporter activity, hydrolase activity, catalytic activity and cell wall modification. The genetic mechanisms that control CI in peach and their implication on breeding for CI resistant peaches will be discussed.